— 17 — JOHS. SCHMIDT 



had taken the young of the polar cod we also found the pelagic young of the arctic pogge, 

 Agonus decugonus, and other more or less distinctly arctic animals, such as Limacina 

 helicina and Calanus hyperboreus. Ciione borealis was also found. 



On the other hand, neither in 1904 nor in 1905 did we find any trace of the pelagic 

 young of the polar cod, though careful search was made for them both in the neighbour- 

 hood of Cape North and at other places where they might be expected to occur, especially 

 in 1904 when our stay at Iceland was extra long. 



From the data it seems to me possible, that the sporadic occurrence of the polar cod 

 on the coasts of Iceland stands in connection with the extent to which the ice covers the 

 coasts, and that its abundance at Iceland will therefore depend upon the latter,' so that 

 in what are called good ice-yoars the young of this species will not be produced at Ice- 

 land, nor will the older specimens be brought down from the Polar Sea. 



However it may be, there is no doubt that even if the polar cod can reproduce in 

 the coldest, ice-covered parts of Iceland, still it is a rare fish there where the Polar Sea 

 and Atlantic meet and is thus obviously at one of the southern boundaries" of its distri- 

 bution, being stopped by the warm Atlantic water; in consequence of this also, it neither 

 reproduces nor even occurs on the warmest coasts of Iceland.-' 



As a distinctly arctic fish which only reproduces in ice-cold water and perhaps even 

 in the neighbourhood of the ice itself, it occupies a characteristic and interesting position 

 amongst the other gadoids mentioned in this work, as its southern boundary lies just 

 where those of its allies which go furthest north are at the northernmost boundary where 

 they reproduce. 



2. Gadus callarias Linné, Cod (Chart I) 



§ 1. Remarks on the identification 



In general there is no difficulty whatsoever in distinguishing the young of the cod at 

 all stages, right from the earliest, just hatched larva so well described and figured by Mc. 

 Intosh and Prince and Mc. Intosh and Masterman, as is mentioned in my Monograph (Gadiis, 

 Part I, p. 9). 



In certain regions, especially in the southern part of the North Sea and W. of Scotland 

 the postlarval stages may be extremely faintly pigmented. The hindmost pigment bar near the 

 end of the tail, which is normally absent in the coalfish (Gadus virens), may thus now and again 

 be quite wanting, and in this way cases of doubt may arise for the less experienced worker. 

 As a rule, however, and amongst other things just because the pigment is on the whole 

 so weak in these specimens of the cod, it can readily be determined whether a coalfish is 

 before one, as its early stages are almost always remarkable for their pronounced pigment- 



> At the parts of Iceland which are always or almost always free ft'om ice, namely the southern 

 and south-western, the polar cod was never found, either as young or as adult. 



^ Other boundaries occur at North America and Northern Norway. 



" I have seen the pelagic postlarval young of Gadus sdida, in addition to those from North Ice- 

 land, also from East Greenland and the White Sea, where they were taken during the Russian investi- 

 gations and were found in a collection of fish young sent me for determination by Dr. Breitpuss. These 

 latter are not included in this work, as they lie beyond its scope. 



3 



